Various proposals have been made concerning diagnosis systems having controllers with a self-diagnosis function for sensor systems.
FIG. 3 is a block diagram showing an example of an existing diagnosis system, and FIG. 4 is a waveform chart which depicts a phase of operation of the system.
In FIG. 3, reference numerals 11 to 19 denote various sensors, reference numeral 2 denotes a controller, reference numeral 3 denotes a lamp, reference numeral 4 denotes an ignition switch, reference number 5 denotes a fuse, reference numeral 6 denotes a battery, reference numeral 7 denotes a connector, and reference numeral 8 denotes a diagnosis switch.
A diagnosis system is a system which performs self-diagnosis for the various sensors 11 to 19, the output signals of which are input to the controller 2. In this example, signals from sensors such as an O.sub.2 sensor 11, a water temperature sensor 12, a throttle sensor 13, an intake air temperature sensor 14, and an air flow meter 15 are input to the controller. Other signals which are input to the controller include a turbo-supercharging pressure signal and an ignition signal.
The result of the diagnosis is displayed by lighting the lamp 3. The diagnostic checking is started by turning on the ignition switch 4 and simultaneously turning on the diagnosis switch 8 provided for the checking (FIG. 4 (a)). A diagnosis code is output by turning the lamp 3 on and off a certain number of times in a certain timing pattern. From among the codes to which the sensors 11 to 19 correspond, a diagnosis code is output three times, in a sequence starting with the smallest code number. For example, in the case of the throttle sensor 13, the lamp 3 is caused to flash in accordance with the code signal shown in FIG. 4 (b) to indicate that a specific abnormality has occurred in the throttle sensor 13.
When a sensor is diagnosed as abnormal during the diagnostic operation, the lamp 3 is lit so as to indicate the abnormality to an operator.
One of the problems of this existing diagnosis system is that, because the exclusive switch 8 has to be provided to actuate the diagnosis function, an increase in production costs results and additional space for the switch is needed.
In addition, although the exclusive connector 7 is provided, it is often the case with this connector that it is not particularly located in a fixed place. Consequently, it has been difficult to find the connector 7 when it is to be used. Further, when there are other connectors, it has been difficult to distinguish with certainty the connector for the diagnosis. If the connector is fixed at a certain location with the view to avoiding these problems, this may again lead to an increase in production costs.
FIG. 5 shows an example of a different existing diagnosis switch. In particular, where no exclusive switch 8 is provided, a short-circuiting connector 80 comprising a lead wire 81 and a connector element 82 ahs to be provided for each operator.
An object of the present invention is to provide a diagnosis switch in which a part of a fuse box is utilized, to thereby solve the problems such as those involving the fixing position and any increase in production costs.